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package runtime
import "core:intrinsics"
udivmod128 :: proc "c" (a, b: u128, rem: ^u128) -> u128 {
_ctz :: intrinsics.count_trailing_zeros;
_clz :: intrinsics.count_leading_zeros;
n := transmute([2]u64)a;
d := transmute([2]u64)b;
q, r: [2]u64 = ---, ---;
sr: u32 = 0;
low :: 1 when ODIN_ENDIAN == "big" else 0;
high :: 1 - low;
U64_BITS :: 8*size_of(u64);
U128_BITS :: 8*size_of(u128);
// Special Cases
if n[high] == 0 {
if d[high] == 0 {
if rem != nil {
res := n[low] % d[low];
rem^ = u128(res);
}
return u128(n[low] / d[low]);
}
if rem != nil {
rem^ = u128(n[low]);
}
return 0;
}
if d[low] == 0 {
if d[high] == 0 {
if rem != nil {
rem^ = u128(n[high] % d[low]);
}
return u128(n[high] / d[low]);
}
if n[low] == 0 {
if rem != nil {
r[high] = n[high] % d[high];
r[low] = 0;
rem^ = transmute(u128)r;
}
return u128(n[high] / d[high]);
}
if d[high] & (d[high]-1) == 0 {
if rem != nil {
r[low] = n[low];
r[high] = n[high] & (d[high] - 1);
rem^ = transmute(u128)r;
}
return u128(n[high] >> _ctz(d[high]));
}
sr = transmute(u32)(i32(_clz(d[high])) - i32(_clz(n[high])));
if sr > U64_BITS - 2 {
if rem != nil {
rem^ = a;
}
return 0;
}
sr += 1;
q[low] = 0;
q[high] = n[low] << u64(U64_BITS - sr);
r[high] = n[high] >> sr;
r[low] = (n[high] << (U64_BITS - sr)) | (n[low] >> sr);
} else {
if d[high] == 0 {
if d[low] & (d[low] - 1) == 0 {
if rem != nil {
rem^ = u128(n[low] & (d[low] - 1));
}
if d[low] == 1 {
return a;
}
sr = u32(_ctz(d[low]));
q[high] = n[high] >> sr;
q[low] = (n[high] << (U64_BITS-sr)) | (n[low] >> sr);
return transmute(u128)q;
}
sr = 1 + U64_BITS + u32(_clz(d[low])) - u32(_clz(n[high]));
switch {
case sr == U64_BITS:
q[low] = 0;
q[high] = n[low];
r[high] = 0;
r[low] = n[high];
case sr < U64_BITS:
q[low] = 0;
q[high] = n[low] << (U64_BITS - sr);
r[high] = n[high] >> sr;
r[low] = (n[high] << (U64_BITS - sr)) | (n[low] >> sr);
case:
q[low] = n[low] << (U128_BITS - sr);
q[high] = (n[high] << (U128_BITS - sr)) | (n[low] >> (sr - U64_BITS));
r[high] = 0;
r[low] = n[high] >> (sr - U64_BITS);
}
} else {
sr = transmute(u32)(i32(_clz(d[high])) - i32(_clz(n[high])));
if sr > U64_BITS - 1 {
if rem != nil {
rem^ = a;
}
return 0;
}
sr += 1;
q[low] = 0;
if sr == U64_BITS {
q[high] = n[low];
r[high] = 0;
r[low] = n[high];
} else {
r[high] = n[high] >> sr;
r[low] = (n[high] << (U64_BITS - sr)) | (n[low] >> sr);
q[high] = n[low] << (U64_BITS - sr);
}
}
}
carry: u32 = 0;
r_all: u128 = ---;
for ; sr > 0; sr -= 1 {
r[high] = (r[high] << 1) | (r[low] >> (U64_BITS - 1));
r[low] = (r[low] << 1) | (q[high] >> (U64_BITS - 1));
q[high] = (q[high] << 1) | (q[low] >> (U64_BITS - 1));
q[low] = (q[low] << 1) | u64(carry);
r_all = transmute(u128)r;
s := i128(b - r_all - 1) >> (U128_BITS - 1);
carry = u32(s & 1);
r_all -= b & transmute(u128)s;
r = transmute([2]u64)r_all;
}
q_all := ((transmute(u128)q) << 1) | u128(carry);
if rem != nil {
rem^ = r_all;
}
return q_all;
}
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